A place of punitive confinement; a lockup or cell; a military guardroom.

(transitive, Internet) To redirect (network traffic, etc.) nowhere; to discard (incoming traffic).

A smooth, barely visible, and dangerously slippery film of ice, usually over a dark surface, such as rock or pavement.

The flanged portion of an oar; not the handle nor the shaft.

A single long, narrow leaf of a plant described by the mass noun grass. / (rare) A very small amount of something.

A thin piece of steel with a sharp edge that can be fitted into a razor. / A replaceable cartridge in which razor blades are set, fitted into a razor.

Either of the large flat bones at the back of the shoulder.

A large flat surface, finished with black slate or a similar material, that can be written upon with chalk and subsequently erased; a chalkboard.

To use a blackboard to assist in an informal discussion.

A person who forges iron. / (informal) A person who shoes horses. / A blackish fish of the Pacific coast (Chromis punctipinnis).